The present invention relates to a high-speed filling machine for filling one or several containers with a predetermined amount of a product, and more particularly to an adjusting mechanism for varying the amount to be dispensed by any type of filling unit into the container connected with the filling unit.
Filling machines of the type to which the present invention relates are known as such in the prior art (U.S. Pat. Nos. 2,807,213 and 2,907,614). In these prior art filling machines, the filling units consisting of a cylinder and piston reciprocating within the cylinder driven by an eccentric drive arrangement. The eccentric pin was operatively connected with the free end of the piston rod such as to allow for a change in the pump stroke and therewith the amount of the product to be dispensed by a given filling unit. For this purpose, the prior art eccentric drives included an adjusting mechanism to vary the amount of eccentricity between the eccentric drive pin and the axis of rotation of the disc-like driving member carrying the drive pin by the use of a lead screw assembly, as more fully disclosed in the aforementioned U.S. Pat. Nos. 2,807,213 and 2,907,614.
While this arrangement proved satisfactory in actual operation for many years, it nevertheless entailed a number of disadvantages. First of all, since the prior art adjusting mechanism for changing the volume of the pump stroke was part of and connected with the rotating disc-like member, any adjustment in the volume of the product to be discharged into the container or containers required a stoppage of the entire filling machine. This drawback became ever more significant as the requirement to improve the overall efficiency of the filling machines became increasingly important, i.e., as the need to increase the speed and to reduce any downtime of the filling machine became ever more important. Moreover, the prior art volume-adjusting mechanisms were relatively complicated in structure thereby increasing the cost of the machine. Additionally, since the adjusting mechanism involved moving parts, subjected to rotation while the machine was operating, the parts of the adjusting mechanism had to be constructed correspondingly strong to be able to withstand the occurring stresses. As a solution to these problems, U.S. Pat. No. 4,227,627 provides the adjustable lost motion; volume adjusting mechanism at the part of the filling unit normally connected with a relatively fixed part of the filling machine.
Finally, when more than one filling unit was operated from a given eccentric drive as disclosed, for example, in the U.S. Pat. No. 4,077,441, the prior art adjusting mechanisms did not permit individual trimming adjustments of the individual filling units to compensate for minor operating differences therebetween. As a solution to this problem, U.S. Pat. No. 4,212,416 provides individually adjustable, lost motion mechanism between a common drive bar and individual filling units.
Although U.S. Pat. Nos. 4,212,416 and 4,227,627 operate efficiently in a variety of applications, there are other applications in which they do not work. To be more specific, when there is a differential pressure across the piston, the lost motion mechanism becomes inoperative. For example, when the liquid to the filling unit is under greater than atmospheric pressure, during the suction or intake stroke, this causes substantial, constant pressure on the product side of the piston which in turn overcomes the frictional drag of the filling unit seals. This effectively locks the lost motion portion, for example, in U.S. Pat. No. 4,212,416 in its lower position with the top of slot 32 engaging the bearing member 33. This is the normal position of the slot and bearing for the discharge stroke of the lost motion mechanism not the suction or intake stroke. Thus, the lost motion mechanism is ineffective. The same problem occurs with the lost motion mechanism of U.S. Pat. No. 4,227,627.
A similar condition occurs in the filling unit as shown in U.S. Pat. 4,569,378, wherein a vacuum is employed to the bottom side of a piston assembly to guarantee the operational integrity of the diaphragm-type seals. This vacuum creates a force on the underside of the piston rather than a positive feed pressure on the upper product side of the piston, but in effect produces the same results of nullifying the lost motion mechanism.
Thus, it is an object of the invention to provide a volume adjusting mechanism including a lost motion which is operable with any kind of filling unit.
Another object of the present invention is to provide a volume adjusting mechanism which can be used with filling units wherein the nonproduct side of the piston is under vacuum.
Still a further object of the present invention is to provide a volume adjusting mechanism including lost motion which can be used with filling units wherein the liquid supply to the filling unit is fed at greater than atmospheric pressure.
These and other objects are attained by providing a counteracting mechanism for acting on a lost motion mechanism of a filling machine to counteract forces between the reciprocal driver and the filling unit to assure that the lost motion mechanism operates with lost motion. The counteracting mechanism is provided between the lost motion mechanism and the driver and is operable during the intake stroke and inoperable during the discharge stroke. The counteracting mechanism includes an actuator acting directly on the lost motion mechanism or through a spring.
The lost motion mechanism includes a first element having an elongated slot and a second element which varies the length of the elongated slot. A third element connected to the driver slides within the elongated slot. The adjustable second element includes a shaft extending from the first element to the driver and the biasing element is mounted around the shaft between the first element and the driver. The shaft is threaded into the first element and extends through the driver. The driver may be a linear reciprocal driver or an eccentric reciprocal driver. Where the filling machine includes a plurality of filling units, each is connected to a common driver by an individual adjustable lost motion mechanism and counteracting mechanism. By the adjustable second element descending beyond the driver, it is readily adjustable during operation.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.